This invention relates to an open-end friction spinning machine having a plurality of spinning units. Each spinning unit has two friction rollers that are arranged next to one another to form a wedge-shaped gap serving as a yarn forming point or region. The friction rollers are drivable in the same rotational direction to carry out spinning operations. Each spinning unit also has a feeding and opening device for the feeding of fibers to the wedge-shaped gap, a suction device for holding the fibers and the forming yarn in the wedge-shaped gap, and a withdrawal device for withdrawing the formed yarn in the longitudinal direction of the wedge-shaped gap.
In order to spin the best possible yarn quality in open-end friction spinning when using differing fiber material, the open-end friction spinning machine is subjected to a basic setting up of spinning conditions that is adapted to that fiber material. In this case, the effect of the suction devices on the wedge-shaped gaps of the spinning units, the circumferential speeds of the friction rollers, the feeding speed of the fiber material, the speed of the opening roller, and the withdrawal speed are adjusted. Even in the case of a good basic adjustment, fluctuations in quality may occur during the spinning of a batch which may be the result of the fact that starting material does not always have the same character and quality, or that temperature fluctuations occur or that the degree of moisture of the starting material is not always the same, or that the fiber mixture and blend fluctuates within one batch, especially in the case of natural fibers and similar materials.
The invention is based on the objective of developing an open-end friction spinning machine of the initially mentioned type in such a way that fluctuations in the quality of the yarn are avoided as much as possible during the operation of the open-end friction spinning machine.
This objective is achieved by equipping each spinning unit with individually adjustable means for changing at least one parameter of the spinning conditions, by providing at least one measuring device for examining the quality of the moving yarn produced at the individual spinning units and by providing an evaluating device for evaluating the signals of the measuring device which, in the case of deviations from indicated desired values, triggers an adjustment of the means for changing at least one parameter of the spinning conditions.
The invention is based, at least in part, on the recognition that in open-end friction spinning, because of the variations in the starting material or of the degree of moisture in the starting material, or similar circumstances, the spinning conditions change especially with respect to the friction effect in the area of the yarn forming point so that either too much twist or--which is even less favorable--too little twist is applied to the yarn. These fluctuations in quality are avoided by changing the friction effect at each spinning unit when diminished quality is determined in such a way that the desired quality value is reached again.
In a development of the invention, it is provided that each spinning unit is equipped with means for adjusting the effect of the suction device. The effect of the suction device is one of the important parameters of the spinning conditions because it determines to a large extent the amount of twist that is applied. When the suction effect is too low, a relatively extensive slip is created between the forming yarn and the shell or cover surfaces of the friction rollers without the application of a sufficient twist to the yarn. When, on the other hand, the suction effect is too high, an excessive twist may be applied.
In a further development of the invention, it is provided that each spinning unit is equipped with a single motor for driving its friction rollers, the speed of which motor can be adjusted. The circumferential speed of the friction rollers is a second important parameter of the spinning conditions in regard to the twist applied to the yarn so that a changing of the speeds of the friction rollers also permits an adaptation of the quality of the yarn to the desired value with respect to the applied twist in a simple manner.
In a further development of the invention, it is provided that each spinning unit is equipped with a measuring device arranged in the travel path of the yarn. In combination with an evaluating device which is permanently connected with the measuring devices, it is therefore possible to continuously monitor the quality of the yarn and to intervene immediately at the respective spinning unit when a need for a change is determined.
In order to reduce technical expenditures for the open-end friction spinning machine, it is provided in a further development of the invention that the evaluating device is arranged in a servicing apparatus that can be moved along the spinning machine and can be selectively applied to the individual spinning units, said servicing apparatus being equipped with adjusting elements for actuating the means for changing at least one parameter of the spinning conditions. In a further development of the invention, the servicing apparatus is equipped with a measuring device that can be applied to the moving yarn of a spinning unit. In this case, only a periodic monitoring of the yarn quality at the individual spinning units is carried out, which in practice will be sufficient in most cases.
In a further development of the invention, it is provided that the measuring device or measuring devices is/are developed as a yarn tension sensor or as yarn tension sensors. Such yarn tension sensors are relatively simple devices which also are relatively precise in their operation. The tension of the yarn can provide information on the twist existing in the yarn so that the tension of the yarn permits a monitoring of the quality of the moving yarn. In this case, it is especially advantageous for the yarn tension sensor or sensors to be applied to the moving yarn in the area between the friction rollers and the withdrawal device. The yarn tension measured at this point provides information on the friction effect in the area of the yarn forming points since the formed yarn is withdrawn against this friction effect. By means of the tension of the yarn, information can therefore be provided on the friction effect and thus on the twist applied to the yarn or the twist deviations with respect to desired value.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, embodiments in accordance with the present invention.